This invention relates to gas velocity and flowmeters.
Velocity measurement devices based on the thermal time-of-flight principle have previously been demonstrated by Bradbury (1971) for turbulent flow measurements and by Wesphal (1981) for measurement of wall shear stresses in gas flow boundary layers. Both of those devices have temperature sensors upstream as well as downstream of the pulse heated wire so as to measure flow direction as well as velocity. That implementation, however, prevents the measurement of gas velocities lower than about 0.3 m/s as reported by both authors. The ability to measure the very low gas velocities is critical in achieving a high velocity measurement range. A high rangeability is essential for residential gas metering applications for natural gas.
A need exists for highly accurate meters which measure gas velocities and flow over wide ranges, and which compensate for variations in gas properties.